1. Field of the Invention
The present invention relates to an endoscope system and more particularly to an endoscope system that outputs an optimal image according to a synchronized state between a phase an image pickup signal and a phase of a reference clock signal.
2. Description of the Related Art
Conventionally, an endoscope system has been constituted by a scope (endoscope) including an image pickup device such as CCD at a distal end portion, and a processor that performs predetermined image processing on an endoscopic image picked up by the image pickup device provided in the scope and displays the processed endoscopic image on a monitor. The scope and the processor are detachably connected to each other via a connector and the like, and different kinds of scopes can be connected to the processor.
The processor in such an endoscope system is provided with a PLL circuit for synchronizing a phase of an image pickup signal inputted from the endoscope and a phase of a reference clock signal which is a reference of a sampling pulse for sampling the image pickup signal.
For example, Japanese Patent Application Laid-Open Publication No. 2007-159991 discloses an endoscope system provided with a PLL circuit that is capable of performing frequency pull-in with a simple configuration with low-phase-noise characteristics being set, in order to perform signal processing adaptable to an endoscope incorporating a high-pixel image pickup device.